Physiological Response And Accumulation Characteristics Of Viola Monbeigii (Violaceae) Under Hg,Pb Stress

This paper takes Viola monbeigii W.Beck,an early spring ornamental with strong ecological adaptability,as the object to study the effect of the heavy metals Hg and Pb stress on seed germination,seedling growth and physiological and biochemical characteristics(such as antioxidant enzymes,cell membrane permeation and etc.)of V.monbeigii and its accumulated characteristics on Hg and Pb,also explore its ecological adaptability on Hg and Pb stress and possible tolerance mechanism,with a view to the ecological restoration of Hg and Pb contaminated soil provide theoretical basis and practical guidance.The main results are as follows:Under the treatment of Hg stress,the germination rate and seedling growth of V.monbeigii are both not significantly affected at low concentrations,but will be significantly inhibited at high concentrations.The seedlings begin to die at a concentration of 5 mg/L,and with the increase of the Hg stress concentration,seedling mortality goes up obviously.The root vigor of V.monbeigii presented earlier increase and later decrease trend with Hg stress concentration keeps increasing.When the Hg stress concentration is 10 mg/L,the root vigor reaches the maximum;and with the increase of Hg concentration,the cell membrane permeability shows a trend of increasing first and then decreasing and increasing,at this time,the membrane permeability will reduce to the minimum at 10mg/L.When the concentration of Hg stress is in the range of 5-10 mg/L,the soluble protein content of V.monbeigii leaves is the largest,and the peak of the root system appears at 2-5 mg/L.GSH in V.monbeigii was significantly affected by Hg Stress,and its content decreased with the increase of Hg Stress.Under Hg stress,the CAT activity of V.monbeigii leaves goes up first and then goes down,and the maximum value appears at the Hg stress concentration of 2 mg/L;the enzyme activity of the root system also shows the same tendency and the enzyme activity is significantly higher than the blade part which was treated with the same concentration.POD activity presents a tendency of increasing first and then decreasing.The SOD activity of the leaves also shows a trend of increasing first and then decreasing.The maximum value appears at the Hg stress concentration of 5 mg/L.At high concentrations,the enzyme activity is significantly inhibited.Under low concentration of Hg stress(2mg/L),the parameters of Fv'/Fm',Y(II),qP and NPQ of the leaf of V.monbeigii reach the maximum,and then decrease significantly with Hg increasing concentration.V.monbeigii has a certain accumulation capacity for Hg,with the increasing of Hg concentration,the accumulation of Hg in V.monbeigii significantly increase too.Under the stress of V.monbeigii concentrations,the translocation coefficient of V.monbeigii to Hg is in the range of 0.51-0.97,which not reach the standard of hyperaccumulator plants.(4)Low concentration of Pb has no obvious effect on the seed germination and seedling growth of V.monbeigii,with increasing of stress concentration,seed germination and seedling growth are significantly inhibited.The stress at all concentrations will not cause the seedlings to die.(5)Under Pb stress,the root vigor of V.monbeigii shows a trend of increasing first and then decreasing with the increase of Pb concentration.When the Pb stress concentration reaches 700 mg/L,the root activity achieves the maximum;the membrane permeability will rise at 300 mg/L,and then change little with the increase of Pb concentration.The soluble protein of the leaves is the largest in the range of 500-700mg/L,and the peak of the root system appears at 300-500mg/L.The leaf CAT activity of V.monbeigii shows a negative correlation with the Pb concentration,while the enzyme activity of the root system shows a trend of increasing first and then decreasing.When the Pb stress concentration reaches 300 mg/L,the activity is the largest;changes of POD activity in the leaves also shows the same trend as the root enzyme activity,but the overall enzyme activity of the leaves is significantly lower than that of the root system.The SOD activity of the leaves decreases with the increase of Pb stress concentration,and the SOD activity of the root system increased first and then decreased.The maximum value appears at the Pb stress concentration of 300 mg/L.Under Pb stress,photosynthetic fluorescence parameters show a trend of increasing first and then decreasing.Under certain concentration of Pb stress(50-500mg/L),photosynthetic capacity increased significantly.Fv'/Fm',Y(II),qP and NPQ reache peak within the scope.(6)V.monbeigii has a strong accumulation characteristic for Pb.With the increase of Pb concentration,the accumulation amount increases significantly and mainly accumulates in the aerial part.The maximum accumulation amount is 179m/kg.V.monbeigii has a very high transport coefficient for Pb,and the transport coefficient of V.monbeigii under all stress concentrations is greater than 1,reaching the standard of hyperaccumulator plants.In summary,V.monbeigii shows good tolerance to low-concentration Hg(2-10mg/L)stress,but under high-concentration Hg(40-80mg/L)stress,germination and physiological activities are significantly inhibited;Although there is a certain accumulation capacity for Hg,the main accumulation site is at the root,but the transport capacity is relatively weak.V.monbeigii is highly tolerant to Pb stress and has a very high transport super-enrichment capacity for Pb.Therefore,V.monbeigii can be used as a heavy metal repair plant in Lanzhou or similar areas.